“Air Caraïbes Flight 1501”的意思、由来-开放百科全书

Air Caraïbes Flight 1501 (TX1501/FWI1501) was a scheduled international passenger flight, flying from Saint Martin Airport in the Dutch overseas territory of Sint Maarten to Saint Barthélemy Airport in the French overseas region of Guadeloupe. The flight was operated by Air Caraïbes, a Caribbean regional airline, using a de Havilland Canada DHC-6-300 Twin Otter. On 24 March 2001, during an approach to Saint Barthélemy Airport, the DHC-6 Twin Otter banked steeply to the left and crashed onto a house, killing all 19 passengers and crews on board. One person on the ground was also killed in the explosions that followed.

The crash was the third deadliest plane crash in Guadeloupe, behind Air France Flight 212 and Air France Flight 117, and was the 11th deadliest involving a Twin Otter.

Investigation by the French BEA (short for Bureau d'Enquêtes et d'Analyses pour la Sécurité de l'Aviation Civile ) concluded that the cause of the crash was due to the crew error in managing the thrust lever of the aircraft. During its final approach to Saint Barthélemy, the crew accidentally caused the aircraft to enter its BETA range by moving the thrust lever back to the Beta range, creating a thrust asymmetry which caused the aircraft to bank steeply to the left and crash.

According to the BEA, this was the first fatal accident in the Twin Otter whereby an accidental thrust selection caused a propeller to enter the Beta range. The investigation was hampered as there was no flight recorder installed on the plane. After the crash, the BEA made mandatory recommendation(s) to equip every transport plane with at least one flight recorder.

Flight

Take-off and approach

Flight 1501 took off from Princess Juliana International Airport at 04:00 pm local time, using a Visual flight rules (VFR) flight plan, and was expected to land in Saint Barthélemy at 04:15 pm. The distance between Saint Martin and Saint Barthélemy is approximately {{convert|19|nmi|km mi|abbr=on}}. Weather was reported as good, with calm winds and very good visibility.^[1]

The flight entered its cruise altitude of {{convert|1500|ft|abbr=on}} and the crew reported passing the "Pain de Sucre" way-point for a final approach to runway 10 of Gustaf III Airport in the last transmission from Flight 1501.^[2]^[1]

Crash

While flying above the Western slope of La Tourmente Pass, the aircraft suddenly banked steeply to the left.^[1] Numerous eyewitnesses including an Aerodrome Flight Information Service (AFIS) worker claimed that Flight 1501 then rapidly lost altitude and crashed onto a house, with a massive explosion following immediately after impact. Emergency services quickly arrived to the scene and cordoned the area. All 19 people on board were killed instantly in the crash and an elderly man, identified as Augustin Questel,^[3] who lived inside the house with his wife, died from the subsequent fire and explosion. His wife was alive but slightly injured, and was taken to hospital.^[4]

Aircraft

The aircraft involved was a de Havilland Canada DHC-6-300 Twin Otter, popular among regional airlines operating short routes. Registered in France as F-OGES (msn 254), the aircraft was equipped with two Pratt & Whitney Canada engines driving Hartzell propellers.^[1] It entered into service with Air Guadeloupe in 1970, was subsequently sold to Air Caraïbes and had accumulated a total of 35,680 flying hours and 89,331 flight cycles.^[5]^[1]

Passengers and crews

According to local manager of Air Caraïbes, most of the passengers were French tourists,^[6] with 2 local residents of Saint Barthélemy, 15 French residents of Paris and one American, according to Air Caraïbes CEO Philippe Chevallier.^[4]^[2] One of the crew members was a French national while other's nationality was not revealed. Multiple reports stated that one Dutch woman and two Belgians were also on board. The American was also reported to have dual nationality.^[7]^[8]

The pilot flying obtained his commercial pilot license on 18 June 1987 and Instrument Rating on 3 November 1987. He obtained DHC-6 type rating on 28 November 1988 and was subsequently hired as a pilot by Air Guadeloupe and later transferred to Air Caraïbes. The Captain had acquired a total flying hours of 9,864 hours, of which 5,000 hours were on Twin Otters. He was later identified by Air Caraïbes' official as Jean-Paul Jerpan.^[3]^[1]

The co-pilot obtained his Twin Otter type rating on 21 December 2000, having had previous professional experience as a flight engineer in the French Air Force. According to the investigators, he was employed on a short-term contract, in which he was supposed to join another airline as a flight engineer. He had acquired a total flying hours of 670 hours of which 15 of them were on the DHC-6.^[1]

Investigation

As the crash occurred within the French territory, the BEA was responsible for the investigation. The BEA sent two field investigators to the crash site and later sent four investigators to Pointe-à-Pitre on 25 March. As the aircraft was manufactured in Canada, the Canadian TSB (Transportation Safety Board) joined the investigation with the assistance from Bombardier and Pratt and Whitney Canada. The American NTSB (National Transportation Safety Board) also joined the investigation and sent a correspondent for the investigation.^[1]

According to Philippe Chevallier, the CEO of the airline, the aircraft was not equipped with a black box,^[9] and thus investigators had to rely on observations of air traffic controller recordings, eyewitnesses, wreckage observation and their best guess on what might have happened on Flight 1501. Airport officials quickly claimed that mechanical failure caused the crash. One witness stated that he heard an engine "sputtering" before the aircraft slammed onto the house.^[1]^[2]

The Saint Barthélemy Airport is surrounded by the La Tourmente Pass, requiring pilots to have special certification to land there. Aircraft approaching the runway must make a steep descent and fly low over houses before landing, with no night flights and all aircraft to be equipped with radio.^[1]

On the first phase of the investigation, investigators inspected the wreckage of the plane. Initial examination revealed that there were no signs of abnormalities on the plane's controls. Inspection on the plane's propellers also revealed that both propellers were delivering significant power during the crash. Due to the severity of the impact, investigators could not take fuel sample from the wreckage. During their inspection, they found two video cameras from the crash site.^[1]

Deeper observation on the plane's propellers revealed that the left propeller had a pitch setting of at least 20.4°, that is to say a pitch superior to that of flight idle. The right propeller had a different pitch setting for each of the blades, settings likely due to less violent secondary impacts on the powerplant at the moment of the accident. Consequently, the values noted were unusable.^[1]

Use of video camera on the investigation

The footage recovered from the crash site by investigators would make a significant step in the investigation. Of the two video cameras recovered, one of them was too badly damaged by the impact that investigators could not do anything to repair the film. However, the second one was less damaged and it could be fixed by investigators, although the part which covered the recording heads as well as one part which had likely been recorded on was damaged by the fire.^[1]

Investigators started an examination on the flight based on the video taken by one of the passengers of Flight 1501. The video had been filmed through a left-side window and that the film, with titles, had been made a few minutes before the accident. During its playback, investigators examined the three main sequence of the flight: initial climb, cruise, and approach. Investigators later analysed the video more thoroughly on the propeller's operation.^[1]

They made an analysis on the plane's propeller sound. During Flight 1501's initial climb and cruise, there were no abnormalities on the propellers' sound. However, during its approach they did find an abnormality. Investigators stated that there were fluctuations on the propeller, and stated that both propellers were "not synchronized".^[1]

Flights observation and footage comparison

Investigators later made an observation on commercial flight. The observation would use the same video camera with the one they had recovered before, and would evaluate the track, engine parameters, and the pilot's hands position. The hand position was observed by investigators as the thrust lever of the DHC-6 was located on the ceiling. Investigators would like to know if this issue could contribute to the crash.^[1]

It was revealed that, when the pilot flying was seated on the left, his right forearm is located in the extended vertical axis of the levers, a position which is favorable to symmetric handling. However, when the pilot flying is seated in the right position, his left forearm is not vertical; he stretches slightly to the left and is thus not aligned with the axis of the levers, this "angle" being compensated by wrist movement. In addition, if the pilot flying was seated on the right, he would move the thrust lever on a different timing, used short successive and separate movements on the engine no.1 lever, then on the engine no.2 lever, with the hand always remaining in contact with both levers.^[1]

A comparison was made by investigators and confirmed the position of Flight 1501. An analysis on the engine parameters also showed that both were functioning normally during its take-off until the last image of the video, recorded just minutes before the accident. Towards the end of the film, the spectral analysis showed an increase in the propeller speed. This variation seems to correspond to the beginning of the descent towards the airport, at the moment when the crew selected the propeller full low pitch position.^[1]

Thrust lever BETA

In the DHC-6, there is a mode called as "beta", where the crews could control the propeller pitch directly. There are two ranges of beta; the first one is a range from + 17° to + 11°, called "approach beta" and permitted in flight. In this range, the propellers are tractive. The second one is a range from + 11° to - 15°, called "reverse beta" which is prohibited in flight. In this range, the propellers act as brakes, two different sub-ranges being identifiable: ground idle and traction reversal. If the reverse beta was retracted in mid-air, based on the manufacturer, this could produce a high amount of drag which would result in a significant loss of speed. Subsequently, the plane could lose its lift.^[1]

The manufacturer had known about this risk since 1979 and had started to implement several preventive measures. They had warned pilots about the risk in every flight manuals. They had installed a mechanical stop to ensure pilots to not causing their plane to enter the beta range. An alarm had also been installed by the manufacturer.^[1]

Investigators' hypotheses

Investigators made several hypotheses on Flight 1501. Mechanical failure, terrorism, bird strike and weather related factor were quickly ruled out by investigators. They focused their attention on two strong hypotheses.^[1]

The first one was that the pilot flying, the Captain, had accidentally selected the reverse beta range for the propellers with the intention of losing energy to correct the airspeed, regain the descent path or shorten the landing as much as possible, as the reverse beta mode acted as powerful brakes. During that time, an asymmetry occurred, which could have caused an undesirable behavior or could have caused the plane to reach its desired speed. In either case, it is necessary at that moment to de-select reverse beta range. Then the pilot would have pushed the levers energetically back to their normal use range by increasing the thrust, which would explain the change in the engine noise. Asymmetry in the power levers movement, or in the operation of the propeller mechanism, or even in the position of the propeller levers, would then have led to asymmetry between the engines, to an extent that would have led to a violent yaw movement, inducing a sharp roll to the left, possibly associated with a stall of the left wing, then a dive. The pilot would not have been able to regain control of the aircraft, which would have been both too slow and too near the ground at that moment. This hypothesis was supported by testimonies from numerous eyewitnesses and routine in-flight procedure violations in the airport.^[1]

The second one was that the pilot flying was the co-pilot. One day before the crash, the co-pilot had performed a take-off from Saint Barthélemy. The Captain, who was more experienced than the co-pilot, ordered the co-pilot to conduct the approach, without himself taking over radio communications with the tower. The co-pilot was seated on the right, where it was not easy to control the thrust lever.^[1]

However, according to the investigators, both hypotheses could or could not be excluded since there were no flight recorders that could confirm these hypotheses. They did believe that the first one was far more probable, based on testimonies of eyewitnesses, and concluded that the most probable cause of the crash was due to the selection of the reverse beta range.^[1]

Conclusion

The investigation could not exclude three other hypotheses which can nevertheless be classified as quite unlikely:

The Captain's lack of recent experience on this airplane type, the undeniable difficulty of conducting an approach to runway 10 at Saint-Barthélemy and the pressure of time during this flight were contributory factors.

The low height at which the loss of control occurred was an aggravating factor.^[1]}}

The absence of flight recorder

The investigation was hampered due to the absence of a cockpit voice recorder and a flight data recorder. BEA made a statement:^[1]

After the crash, the BEA made mandatory recommendation(s) to the DGAC (Directorate General for Civil Aviation) and to the JAA (Joint Aviation Authorities) to equip every public transport plane authorized to carry more than nine passengers and whose maximum certified take-off weight is less than or equal to 5,700 kg, with at least one flight recorder. The BEA stated that the recommendation should be implemented as soon as possible and stated that the recommendation should also be applied for cargo plane and helicopters.^[1]

Aftermath

Immediate response

The President of France Jacques Chirac sent a message of condolence to the families of the victims. The then Prime Minister of France Lionel Jospin and Foreign Secretary Christian Paul also expressed their "emotion" and "deep sadness" to the families of the victims later on 25 March.^[10] The Mayor of Saint Barthélemy Bruno Magras, and, according to the will of Saint Barthélemy's people, declared Monday 26 March as a day of official mourning, dedicated for the victims of the crash. Schools, public services, and most businesses would be closed on that day. A prayer service was held in Gustavia, the island's most important town, on 25 March. According to the General Manager of Air Caraïbes, Philippe Chevallier, the airline would fly relatives of the victims to the crash site.^[10] The prefect of Guadeloupe immediately went to the scene to organize relief: reinforcements of gendarmerie and firemen as well as teams of psychologists were sent to the scene.^[10]^[11]

Lawsuit

A hearing dedicated for the crash was opened at the Correctional Court of Basse-Terre in Guadeloupe on 29 June 2006. The hearing would last for two days. The case stated that there were alleged criminal offences. Richard Degryse, who was responsible for the training of Air Caraïbes at the time of the events, was charged with involuntary manslaughter. Jean-Paul Dubreuil, the president of the company, who was also charged with manslaughter, would also appear on the court.^[12]

Twenty-one members of the association of families of victims, Adfv, chaired by Karine Paris, arrived in Guadeloupe with their three lawyers who also represent the National Federation of victims of collective accidents. Other civil parties would also be at the trial, including members of the Questel family.^[12]

On 15 September 2006, Richard Degryse was convicted guilty for involuntary homicide and was sentenced for two years of prohibition from exercising a professional activity in connection with the direction of flight operations.^[13] The sentence was far less than what the prosecutor had demanded, who had demanded for a two-year prison sentence with a suspended sentence, as well as a five-year ban. Subsequently, the airline, Air Caraïbes, was also convicted guilty and was fined 250,000 euros by the court.^[13] The court would have considered that the operations manager as well as the company knew that they had formed a dangerous crew for failing to comply with the training flight requirement for a pilot taking control of an aircraft more than 90 days after leaving . The court also received the civil party constitutions - after 70 - whose interests would be examined during a civil lawsuit, held on December 22 at the tribunal of Basse-Terre.^[13]